Asserter has new methods ResponseStatusCodeIsSuccess and ResponseBody…

…IsEmpty, small updates

CreateHttpRequest override that accepts HttpRequest object

Upload files with multipart content type

Added NTLM authentication and small updates

* nullable check

* readme update

* Added NTLM authentication

* small asserter refactoring and readme file updates

* version bump

tests fix

JSON body can be passed as string, logo and test update

* logo and test update

* Httptester client updates

* JSON body can be passed as string, small bug fixes and new tests

merge conflict resolved

disposable pattern implemented for main object, version bump and readme